Mobile communications has changed the way people communicate and mobile phones have been transformed from a luxury item to an essential part of every-day life. The use of mobile phones is today dictated by social situation, rather than by location or technology. While voice connections fulfill the basic need to communicate, and mobile voice connections continue to filter even further into the fabric of life, the mobile Internet is the next step in the mobile communication revolution. The mobile Internet is poised to become a common source of information, and easy, versatile mobile access to this data will be taken for granted.
Third generation (3G) cellular networks have been specifically designed to fulfill these future demands of the mobile Internet. As these services grow in popularity and usage, factors such as cost efficient optimization of network capacity and quality of service (QoS) will become ever more essential to cellular operators. These factors may be achieved with careful network planning and operation, improvements in transmission methods, and advances in receiver techniques. To this end, carriers need technologies that will allow them to increase downlink throughput and, in turn, offer advanced QoS capabilities and speeds that rival those delivered by cable modem and/or DSL service providers. In this regard, networks based on wideband CDMA (WCDMA) technology can make the delivery of data to end users a more feasible option for today's wireless carriers.
WCDMA has evolved continuously towards higher data rates and towards packet-switched IP-based services. The following paragraphs elaborate on the evolution to HSDPA from GPRS via EDGE.
The GPRS and EDGE technologies may be utilized for enhancing the data throughput of present second generation (2G) systems such as GSM. The GSM technology may support data rates of up to 14.4 kilobits per second (Kbps), while the GPRS technology may support data rates of up to 115 Kbps by allowing up to 8 data time slots per time division multiple access (TDMA) frame. The EDGE technology, a further enhancement to GPRS, may support data rates of up to 384 Kbps. The EDGE technology may utilizes 8 phase shift keying (8-PSK) modulation to provide higher data rates than those that may be achieved by GPRS technology. The GPRS and EDGE technologies may be referred to as “2.5G” technologies.
The UMTS technology with theoretical data rates as high as 2 Mbps, is a 3G evolution of GSM, using wideband CDMA technology. UMTS may achieve higher data rates than GSM/EDGE due to many enhancements, including higher transmission bandwidth, adaptive higher order modulation and interference averaging due to a unity frequency reuse factor.
The High-Speed Downlink Packet Access (HSDPA) technology is an Internet protocol (IP) based service, oriented towards data communications, which adapts WCDMA to support data transfer rates in the order of 14 megabits per second (Mbit/s). Developed by the 3G Partnership Project (3GPP) group, the HSDPA technology achieves higher data rates through a plurality of methods. In order to avoid excessive interference, 2G WCDMA may require fast power control to maintain a constant data rate. The HSDPA technology changes this paradigm and instead maintains a constant transmission power but may change the coding and modulation rate to adapt to changing channel conditions. Other methods that may be used to improve the data throughput are fast packet scheduling and a fast retransmission of lost packets by using Hybrid Automatic Repeat Request techniques.
The HSDPA system may consist of a High-Speed Physical Downlink Shared Channel (HS-PDSCH/HS-DSCH), which permits a plurality of users to share the high-speed data connection. Additionally, a plurality of support channels may be available to carry control and setup information. In particular, a plurality of High-Speed Downlink Shared Control Channels (HS-SCCH) may be present. These control channels may carry signaling information for the User Equipment (UE, that is the mobile terminal) and may contain information about when the UE may expect data and how the data will be encoded.
Since processing of the HS-SCCH channel takes place at the UE, these operations may be very sensitive to power consumption. However, lowering the quality of the signal processing in order to save energy, may lead to more significant power expenditure due to incorrect decisions taken. For example, this may be the case when the UE erroneously changes from stand-by mode to HS-PDSCH receiver mode based on incorrectly decoded HS-SCCH data. It is therefore important to devise methods that may lead to a minimum of errors in the decoding of the HS-SCCH and that may use a minimum of power.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with some aspects of the present invention as set forth in the remainder of the present application with reference to the drawings.